1. Field of the Invention
This invention relates to acid- or anhydride-modified polyester-based adhesives suitable for bonding a variety of substrates, particularly thermoplastic polyester and gas-barrier polymers. The adhesives and composite structures made therewith are particularly useful for making laminated containers and package structures.
More particularly, the invention relates to elastomeric polyester-based adhesives that are particularly suitable for bonding polyester structural layers to layers of ethylene-vinyl alcohol copolymer, polyamide, or other polar gas barrier material to form composite structures that are particularly useful for food and drink packaging purposes.
2. Related Technology
Various modified polyester resin materials have been suggested for a variety of uses.
Salgado, et al., U.S. Pat. No. 3,232,893 (Feb. 1, 1966) discloses acid- or anhydride-modified polyester foams having good strength properties useful for foamed-in-place applications.
Fydelor, U.S. Pat. No. 4,148,839 (Apr. 10, 1979) discloses a polyester or other polymer having a crosslinked carboxylic acid graft on its surface, with chemically bound metal atoms or ions in the surface region thereof, useful as membrane separators and in other applications where plastics or other polymeric materials having reduced liquid solvent or gas permeability are required.
Gaylord, U.S. Pat. No. 4,506,056 (May 19, 1985) discloses a process for preparing a maleic acid- or anhydride-modified polyester in the absence of solvents by grafting maleic anhydride to the polymer at a temperature above the melting point of the polymer in the presence of a free radical initiator. Maleic anhydride homopolymerization is inhibited by the addition of various nitrogen, phosphorus or sulfur compounds.
The foregoing disclosures exemplify a variety of polyester reaction mixtures and uses of the polyester-containing products. Acid- or anhydride-modified elastomeric polyester adhesives and their use in bonding thermoplastic polyester films or sheets to polar gas-barrier films of polymers such as ethylene-vinyl alcohol polymers and the like are not disclosed.